First, make sure you're running the newest version of HTC Sync 3.0.5511 for the Evo from here:
HTC Mobile Phone Support - HTC EVO.
Leave your phone in disk drive mode when you first connect to be sure you can see your SD card on your computer. That takes a minute or two on my computer, and the Sync error message you showed will probably pop up too.
If that works, while still connected, switch the phone to HTC Sync and in another 30 seconds to a minute, HTC Sync should pop up.
Correction: Link to newest version 3.0.5517 here:
http://forum.ppcgeeks.com/htc-evo-4g...-0-5517-a.html